Insulin is a hormone made in your pancreas, which is a gland behind the stomach. It helps your body use glucose (sugar) for energy.
When your pancreas is working properly it makes small amounts of insulin all the time and releases more insulin when your blood glucose levels increase after eating. When you have diabetes, your body does not make enough insulin or the insulin it makes does not work properly.
Everyone with type 1 diabetes, and some people with type 2 diabetes or gestational diabetes, needs to take insulin to help manage their blood glucose levels. This reduces the chances of getting the symptoms of high blood glucose (hyperglycaemia) and serious long-term problems that can damage the heart, kidneys, eyes, nerves and feet.
Rapid-acting insulin is a type of very fast-acting insulin. This means it starts to work very quickly and you take it before meals to stop your blood glucose from going too high when you eat carbohydrates.
Rapid-acting insulin is sometimes also known as bolus insulin or mealtime insulin.
Unless you use an insulin pump, you'll usually take rapid-acting insulin along with another type of insulin called intermediate-acting insulin or long-acting insulin. This is taken once or twice a day and gives you the background insulin you need when you're not eating.
Rapid-acting insulin is available on prescription only. It comes as:
- pre-filled pens
- cartridges that you use in a reusable insulin pen
- cartridges that you use in an insulin pump
- a solution in a vial (a small bottle) for injecting or using in a pump
Rapid-acting insulin types, brands and pens
There are 3 different types of rapid-acting insulin:
- insulin aspart (Fiasp, NovoRapid and Trurapi)
- insulin glulisine (Apidra)
- insulin lispro (Admelog, Humalog and Lyumjev)
They come in different brands and are used with different types of insulin pen, but they all work in a similar way. Some brands work more quickly than others.
They all come as injections containing 100 units of insulin per 1ml. Humalog and Lyumjev also come as injections containing 200 units of insulin per 1ml.
Key facts
- Rapid-acting insulin starts to work after about 10 to 20 minutes and lasts for up to 5 hours. You'll usually take it around 15 minutes before a meal but it can be taken up to 10 minutes after a meal.
- Your doctor or diabetes nurse will tell you how much rapid-acting insulin to take. You may need to adjust your dose depending on the amount of carbohydrates in your meal (carb counting).
- Insulin treats the symptoms of diabetes by lowering your blood glucose. But it can sometimes cause your blood glucose to go too low. This is known as hypoglycaemia, or hypos. Make sure you know the symptoms of a hypo, and always carry a source of glucose with you, such as sugary sweets, in case you need to treat a hypo.
- It's a good idea to carry medical identification such as an insulin safety card or insulin passport – a small card with up-to-date details of the type of insulin you use, and what to do in an emergency.
- If you have diabetes, you're entitled to free prescriptions for all your medicines, not just your insulin.